Astronomy FOR DUMmIES ‰ 3RD EDITION by Stephen P. Maran, PhD Astronomy FOR DUMmIES ‰ 3RD EDITION Astronomy For Dummies®, 3rd Edition Published by John Wiley & Sons, Inc. 111 River St. Hoboken, NJ 07030-5774 www.wiley.com Copyright © 2013 by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permit- ted under Sections 107 or 108 of the 1976 United States Copyright Act, without the prior written permis- sion of the Publisher. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748- 6008, or online at www.wiley.com/go/permissions. 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For general information on our other products and services, please contact our Customer Care Department within the U.S. at 877-762-2974, outside the U.S. at 317-572-3993, or fax 317-572-4002. For technical support, please visit www.wiley.com/techsupport. Wiley publishes in a variety of print and electronic formats and by print-on-demand. Some material included with standard print versions of this book may not be included in e-books or in print-on-demand. If this book refers to media such as a CD or DVD that is not included in the version you purchased, you may download this material at http://booksupport.wiley.com. For more information about Wiley products, visit www.wiley.com. Library of Congress Control Number: 2012948997 ISBN 978-1-118-37697-3 (pbk); ISBN 978-1-118-37694-2 (ebk); ISBN 978-1-118-37695-9 (ebk); ISBN 978-1-118-37696-6 (ebk) Manufactured in the United States of America 10 9 8 7 6 5 4 3 2 1 About the Author Stephen P. Maran, PhD, a 36-year veteran of the space program, has been honored with the NASA Medal for Exceptional Achievement. He received the Klumpke-Roberts Award of the Astronomical Society of the Pacific for “outstanding contributions to the public understanding and appreciation of astronomy,” the George Van Biesbroeck Prize of the American Astronomical Society, for “long-term extraordinary or unselfish service to astronomy,” and the Andrew W. Gemant Award of the American Institute of Physics for “significant contributions to the cultural, artistic, or humanistic dimension of physics.” In 2000, the International Astronomical Union named an asteroid (Minor Planet 9768) “Stephenmaran” for Dr. Maran. Dr. Maran began practicing astronomy from rooftops in Brooklyn and at a deserted golf course in the far reaches of the Bronx. He graduated to conduct professional research with telescopes at the Kitt Peak National Observatory in Arizona, the National Radio Astronomy Observatory in West Virginia, the Palomar Observatory in California, and the Cerro Tololo Inter-American Observatory in Chile. He also conducted research with instruments in space, including the Hubble Space Telescope and the International Ultraviolet Explorer. He helped design and develop two instruments that flew in space aboard Hubble. He’s also taught astronomy at the University of California, Los Angeles, and the University of Maryland, College Park. As press officer of the American Astronomical Society for many years, he presided over media briefings that brought news of astronomical discoveries to people worldwide. Dr. Maran observed total eclipses of the sun from the Gaspé Peninsula and elsewhere in Quebec; Baja California in Mexico; the Sahara desert in Libya; at sea off New Caledonia and Singapore in the eastern Pacific; and the shores of the U.S. In the course of spreading the good word about astronomy, Maran has lectured on black holes in a bar in Tahiti and explained an eclipse of the sun on NBC’s show. He’s also spoken on eclipse and comet cruises aboard Cunard’s and Sitmar Line’s , and MSC Cruises’ Sinfonia. He’s addressed audiences ranging from inner-city Seattle school children and Atherton, California, Girl Scouts to the National Academy of Engineering in Washington, D.C. and subcommittees of both the U.S. House of Representatives and the U.N. Committee on the Peaceful Uses of Outer Space. Dr. Maran is editor of and has co-authored or edited ten other books on those subjects, including two recent works written jointly with Laurence A. Marschall, and He has written many articles for and magazines and served as a writer and consultant for the National Geographic Society and Time-Life Books. Dr. Maran is a graduate of Stuyvesant High School in New York City (where he served a full season on the Math Team without incurring serious injury) and of Brooklyn College. He received both his MA and PhD in astronomy from the University of Michigan. Maran is married to Sally Scott Maran, a journalist. They have three children. Dedication To Sally, Michael, Enid, and Elissa with all my love. Author’s Acknowledgments Thanks first to my family and friends who put up with me in the writing of this book. Thanks also to my agent, Skip Barker, who goaded and guided me in this project, and to Stacy Collins for her faith in the original project and Lindsay Lefevre for championing this substantially revised edition. I’m grateful to Ron Cowen and Dr. Seth Shostak for their past contributions to this book; to Kathy Cox, Georgette Beatty, Josh Dials, and Jennifer Moore, who organized and edited it; and to their skilled colleagues on the editorial and production teams at Wiley Publishing who made the book better and brighter. A special thanks to Laurence Marschall for suggestions that improved the accuracy and thoroughness of the book. Thanks as well to the organizations that provided the photographs in this book and to the producer of the star maps, Robert Miller. I’m grateful for helpful advice from several experts for this new edition, particularly to Prof. Richard Mushotzky on black holes, Drs. Marc Kuchner and Rory Barnes on exoplanets, and Dr. Shostak on the search for extraterrestrial intelligence. Some drawings in this book have been inspired by Dr. Dinah L. Moche and her excellent book, also published by Wiley. Dr. Moche deserves many thanks for her support of this book and for her dedication to making the science of astronomy accessible to anyone. Publisher’s Acknowledgments We’re proud of this book; please send us your comments at http://dummies.custhelp.com. For other comments, please contact our Customer Care Department within the U.S. at 877-762-2974, outside the U.S. at 317-572-3993, or fax 317-572-4002. Some of the people who helped bring this book to market include the following: Acquisitions, Editorial, and Vertical Websites Project Editor: Jennifer Moore Acquisitions Editor: Lindsay Lefevre Copy Editor: Krista Hansing Assistant Editor: David Lutton Editorial Program Coordinator: Joe Niesen Technical Editor: Laurence A. Marschall Editorial Manager: Carmen Krikorian Senior Editorial Manager: Jennifer Ehrlich Editorial Assistants: Alexa Koschier and Rachelle Amick Art Coordinator: Alicia B. South Cover Photos: Cartoons: Rich Tennant (www.the5thwave.com) Composition Services Project Coordinator: Sheree Montgomery Layout and Graphics: Corrie Niehaus Proofreader: Toni Settle Indexer: Joan Griffitts Publishing and Editorial for Consumer Dummies Kathleen Nebenhaus, Vice President and Executive Publisher David Palmer, Associate Publisher Kristin Ferguson-Wagstaffe, Product Development Director Publishing for Technology Dummies Andy Cummings, Vice President and Publisher Composition Services Debbie Stailey, Director of Composition Services Contents at a Glance Introduction ................................................................ 1 Part I: Stalking the Cosmos .......................................... 5 Chapter 1: Seeing the Light: The Art and Science of Astronomy .................................7 Chapter 2: Join the Crowd: Skywatching Activities and Resources ..........................27 Chapter 3: The Way You Watch Tonight: Terrific Tools for Observing the Skies ......45 Chapter 4: Just Passing Through: Meteors, Comets, and Artificial Satellites ..........65 Part II: Going Once Around the Solar System ............... 85 Chapter 5: A Matched Pair: Earth and Its Moon ..........................................................87 Chapter 6: Earth’s Near Neighbors: Mercury, Venus, and Mars ..............................109 Chapter 7: Rock On: The Asteroid Belt and Near-Earth Objects .............................129 Chapter 8: Great Balls of Gas: Jupiter and Saturn ......................................................139 Chapter 9: Far Out! Uranus, Neptune, Pluto, and Beyond ........................................151 Part III: Meeting Old Sol and Other Stars .................. 161 Chapter 10: The Sun: Star of Earth ..............................................................................163 Chapter 11: Taking a Trip to the Stars ........................................................................187 Chapter 12: Galaxies: The Milky Way and Beyond ....................................................217 Chapter 13: Digging into Black Holes and Quasars ...................................................241 Part IV: Pondering the Remarkable Universe ............. 255 Chapter 14: Is Anybody Out There? SETI and Planets of Other Suns .....................257 Chapter 15: Delving into Dark Matter and Antimatter ..............................................277 Chapter 16: The Big Bang and the Evolution of the Universe ..................................289 Part V: The Part of Tens ........................................... 301 Chapter 17: Ten Strange Facts about Astronomy and Space ...................................303 Chapter 18: Ten Common Errors about Astronomy and Space ..............................307 Part VI: Appendixes ................................................. 311 Appendix A: Star Maps ..................................................................................................313 Appendix B: Glossary ....................................................................................................321 Index ...................................................................... 325 Table of Contents Introduction ................................................................. 1 About This Book ..............................................................................................2 Conventions Used in This Book .....................................................................2 What You’re Not to Read ................................................................................2 Foolish Assumptions .......................................................................................3 Icons Used in This Book .................................................................................3 Where to Go from Here ...................................................................................4 Part I: Stalking the Cosmos ........................................... 5 Chapter 1: Seeing the Light: The Art and Science of Astronomy . . . . . .7 Astronomy: The Science of Observation ......................................................8 What You See: The Language of Light ..........................................................9 They wondered as they wandered: Understanding planets versus stars .................................................................................10 If you see a Great Bear, start worrying: Naming stars and constellations ............................................................................10 What do I spy? Spotting the Messier Catalog and other sky objects ..............................................................................18 The smaller, the brighter: Getting to the root of magnitudes ........19 Looking back on light-years ................................................................20 Keep on moving: Figuring the positions of the stars.......................21 Gravity: A Force to Be Reckoned With ........................................................25 Space: A Commotion of Motion ...................................................................26 Chapter 2: Join the Crowd: Skywatching Activities and Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 You’re Not Alone: Astronomy Clubs, Websites, Smartphone Apps, and More ..........................................................................................28 Joining an astronomy club for star-studded company ...................28 Checking websites, magazines, software, and apps ........................30 Visiting Observatories and Planetariums ...................................................33 Ogling the observatories.....................................................................34 Popping in on planetariums ...............................................................36 Vacationing with the Stars: Star Parties, Eclipse Trips, Dark Sky Parks, and More .........................................................................37 Party on! Attending star parties .........................................................37 Getting festive at an AstroFest ...........................................................38 Astronomy For Dummies, 3rd Edition xii To the path of totality: Taking eclipse cruises and tours ...............39 Motoring to telescope motels ............................................................41 Setting up camp at dark sky parks ....................................................42 Chapter 3: The Way You Watch Tonight: Terrific Tools for Observing the Skies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 Seeing Stars: A Sky Geography Primer ........................................................46 As Earth turns . . . ................................................................................46 . . . keep an eye on the North Star ......................................................48 Beginning with Naked-Eye Observation .....................................................50 Using Binoculars or a Telescope for a Better View ...................................53 Binoculars: Sweeping the night sky ...................................................53 Telescopes: When closeness counts .................................................57 Planning Your First Steps into Astronomy .................................................63 Chapter 4: Just Passing Through: Meteors, Comets, and Artificial Satellites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65 Meteors: Wishing on a Shooting Star ..........................................................65 Spotting sporadic meteors, fireballs, and bolides ...........................67 Watching a radiant sight: Meteor showers .......................................69 Comets: The Lowdown on Dirty Ice Balls ...................................................74 Making heads and tails of a comet’s structure ................................75 Waiting for the “comets of the century” ...........................................78 Hunting for the great comet ...............................................................80 Artificial Satellites: Enduring a Love–Hate Relationship ..........................82 Skywatching for artificial satellites ....................................................83 Finding satellite viewing predictions ................................................84 Part II: Going Once Around the Solar System ................ 85 Chapter 5: A Matched Pair: Earth and Its Moon . . . . . . . . . . . . . . . . . . .87 Putting Earth under the Astronomical Microscope .......................................88 One of a kind: Earth’s unique characteristics .......................................88 Spheres of influence: Earth’s distinct regions ..................................89 Examining Earth’s Time, Seasons, and Age ................................................93 Orbiting for all time .............................................................................93 Tilting toward the seasons .................................................................95 Estimating Earth’s age .........................................................................97 Making Sense of the Moon ............................................................................98 Get ready to howl: Identifying phases of the Moon.........................99 In the shadows: Watching lunar eclipses .......................................100 Hard rock: Surveying lunar geology ................................................102 Quite an impact: Considering a theory about the Moon’s origin ...........................................................................106 xiii Table of Contents Chapter 6: Earth’s Near Neighbors: Mercury, Venus, and Mars . . . .109 Mercury: Weird, Hot, and Mostly Metal ...................................................109 Dry, Acidic, and Hilly: Steering Clear of Venus ........................................111 Red, Cold, and Barren: Uncovering the Mysteries of Mars ....................113 Where has all the water gone? .........................................................113 Does Mars support life? ....................................................................115 Differentiating Earth through Comparative Planetology ........................117 Observing the Terrestrial Planets with Ease ...........................................118 Understanding elongation, opposition, and conjunction .............119 Viewing Venus and its phases ..........................................................122 Watching Mars as it loops around ...................................................124 Outdoing Copernicus by observing Mercury .................................127 Chapter 7: Rock On: The Asteroid Belt and Near-Earth Objects . . . .129 Taking a Brief Tour of the Asteroid Belt ...................................................129 Understanding the Threat That Near-Earth Objects Pose .....................132 When push comes to shove: Nudging an asteroid ........................134 Forewarned is forearmed: Surveying NEOs to protect Earth .......135 Searching for Small Points of Light ...........................................................136 Helping to track an occultation ........................................................137 Timing an asteroidal occultation .....................................................138 Chapter 8: Great Balls of Gas: Jupiter and Saturn . . . . . . . . . . . . . . . .139 The Pressure’s On: Journeying Inside Jupiter and Saturn .....................139 Almost a Star: Gazing at Jupiter .................................................................140 Scanning for the Great Red Spot ......................................................142 Shooting for Galileo’s moons ...........................................................143 Our Main Planetary Attraction: Setting Your Sights on Saturn .............146 Ringing around the planet ................................................................147 Storm chasing across Saturn ............................................................148 Monitoring a moon of major proportions .......................................148 Making sense of a cryptic moon ......................................................149 Chapter 9: Far Out! Uranus, Neptune, Pluto, and Beyond . . . . . . . . . .151 Breaking the Ice with Uranus and Neptune ..............................................151 Bull’s-eye! Tilted Uranus and its features .......................................152 Against the grain: Neptune and its biggest moon ..........................153 Meeting Pluto, Planet or Not ......................................................................154 The moon chip doesn’t float far from the planet ...........................155 Little Pluto compared to some big moons .....................................156 Buckling Down to the Kuiper Belt .............................................................156 Viewing the Outer Planets ..........................................................................157 Sighting Uranus ..................................................................................158 Distinguishing Neptune from a star .................................................158 Straining to see Pluto ........................................................................159